This invention relates to writing or marking instruments, and more specifically to a writing instrument which permits selective use of a plurality of writing units of different varieties. Still more specifically, the invention deals with such a multiple-point writing instrument comprising a mechanical pencil unit of the pushbutton-action type and at least one other writing unit of a different variety such as, for instance, a ballpoint pen unit.
A multiple-point writing instrument including a mechanical pencil unit, along with a ballpoint pen unit or the like, requires special consideration in the design of its mechanism for the selective feed-out or extension of the writing units to a writing position. This is because, while the ballpoint pen unit or the like is ready for writing or marking when it is fed out to the writing position, the mechanical pencil unit requires further actuation when it reaches the writing position for propelling a lead out of its writing tip. The selective feed-out mechanism must therefore be provided, and functionally associated, with means for propelling a lead out of the mechanical pencil unit when it is in its writing position.
Although a variety of writing unit feed-out mechanisms have been suggested and employed for multiple-point writing instruments of the type in question, they are almost inevitably complex in construction and difficult to manufacture or assemble for the above stated reason, with the resultant increase in the manufacturing costs of the writing instruments themselves. The advent of a truly simple writing unit feed-out mechanism has long been awaited in the stationery industry.